Apparatus and method for cupola ventilation

ABSTRACT

Combustion air entering through the lower portion of the charging opening of a cupola sweeps cupola gas out of the cupola through a gas takeoff duct directly opposite the charging opening and thence to a secondary combustion chamber ahead of a gas cleaning system. Primary burners in the cupola adjacent the charging opening ignite the mixture of cupola gas and combustion air before entry into the gas takeoff duct. The quantity of combustion air is sufficient only to exhaust the cupola gas and to burn the combustible matter contained therein with little or no excess air. The amount of gases to be passed through gas cleaning system is minimized.

United States Patent 721 ln entors Daniel E. Pike 19 Jay St., Harrington Park, 07640; James A. Gross, 62 Yorktown Road, East Brunswick, NJ. 08816 Primary Examiner-Edward G. Favors AttorneyJack Schuman ABSTRACT: Combustion air entering through the lower portion of the charging opening of a cupola sweeps cupola gas out of the cupola through a gas takeoff duct directly opposite the charging opening and thence to a secondary combustion chamber ahead of a gas cleaning system. Primary burners in the cupola adjacent the charging opening ignite the mixture of cupola gas and combustion air before entry into the gas takeoff duct. The quantity of combustion air is sufficient only to exhaust the cupola gas and to burn the combustible matter contained therein with little or no excess air. The amount of gases to be passed through gas cleaning system is minimized.

T0 GAS CLEANING SYSTEM AND FAN SUCTION PATENTEU Amman 3576.381

WW TO GAS CLEANING SYSTEM AND FAN SUCTION INVENTORS DANIEL E. PIKE Y JAMES A. GROSS ATTORNEY APPARATUS AND METHOD FOR CUPOLA VENTILATION BACKGROUND OF THE INVENTION matter contained in said cupola gases.

. 2. Description of the Prior Art Cupolas, commonly constructed with a discharge stack for waste gas and dust above the tall cylindrical cupola structure, are typically used for making high carbon iron by dissolving carbon in low carbon iron, the chemistry of the process being such that reducing, rather than oxidizing, conditions are required inside the cupola. The cupola is provided with an opening for the charging of scrap iron and coke. In the normal course of operation, quantities of obnoxious dust, metallurgical fumes and carbon monoxide are generated which formerly were discharged to the atmosphere through the stack. More recently, the discharge of these waste gases from the cupola through the stack into the atmosphere, being recognized as highly undesirable, was generally forbidden by law. Many communities impose strict controls prohibiting the discharge of such waste gases into the atmosphere and are now rigorously enforcing such controls.

Thus, the operator of a cupola faces two main problems. Firstly, he must collect substantially all of the contaminants produced during normal operation of the cupola to avoid discharging them through the stack into the atmosphere, which means, of course, that he must otherwise dispose of the combustible components such as carbon monoxide by oxidation through the process of combustion. Secondly, he must prevent the formation of an air-carbon monoxide mixture lying within the explosive limits of carbon monoxide within the cupola, as otherwise a violent and destructive explosion within the gas cleaning system may result. If the operator exhausts waste gas from the cupola for subsequent treatment to comply with the law, he risks the entry of air into the cupola through the charging door in such amounts as to create an explosive mixture of carbon monoxide in air. If he brings in sufficient air to form a very dilute mixture of carbon monoxide in air, lying below the lower combustion limit of carbon monoxide in air, he places a heavy burden on the gas treating system because of the huge quantities of air that must pass through the gas treating system along with the cupola gases. if the operator attempts to dispose of the carbon monoxide in or near the melting zone of the cupola by introducing small quantities of air in controlled amounts so as to combust therein carbon monoxide, he has introduced an oxidizing reaction within the cupola which is self-defeating inasmuch as carbon would be burned out of the iron as in conventional steelmaking processes in which the object is to reduce carbon content.

More specifically, current conventional practice is based upon the admission of air in large amounts through the charging opening into the cupola, whereby the cupola gas is swept out of the cupola through a gas takeoff to a gas cleaning and treating system, a fan in such system providing the required draft. The gas takeoff, through which the mixture of cupola gas and air is exhausted from the cupola, is ordinarily located below or above the charging opening. These arrangements have created various problems for the operator, particularly where the gas takeoff is above the charging opening which relative position favors large volumes of air entering the eupola to mix with the waste or cupola gases to be exhausted from the cupola, thereby producing large volumes of gas to burden the gas cleaning and treating system.

'More specifically, a current conventional approach toward the problem of disposing of carbon monoxide gas is to admit large quantities of air through the charging opening and completely burn within the cupola thecarbon monoxide and any other combustible gases that may be evolved from the eupola operation. The burning gases remaining around and above the charging opening generate much useless heat and greatly increase the volume of gases discharged through the stack. The high temperatures caused bythe gases burning in the cupola shorten the life of adjacent metal equipment.

An attempt at solution of the problem is shown in US. Pat. No. 2,6l8,548 (1952) to Drake, wherein is disclosed a sidecharging cupola with a side takeoff pipe adjacent the charging opening. The patent has recognized that, if the entire amount of the gaseous discharge from the stack is to be subsequently treated, it is desirable that the volume of gas so to be treated be held to a minimum. The patent shows a very complex arrangement involving the introduction of secondary air within the cupola below the charging opening at various levels corresponding with the movement of the melting zone during the operation of the cupola. The secondary air is stated as forming combustible mixtures with the carbon monoxide generated above the melting zone, which combustible mixtures burn in the interstices in the charge in the upper portion of the cupola, it being asserted that the heat of combustion preheats the charge of coke and scrap iron and also lowers the concentration of carbon monoxide adjacent the charging opening so that this gas is no longer combustible or explosive. When the charging door is open, fresh air drawn in from the atmosphere, due to the suction of the fan in the cleaning system, is stated as not causing the burning or explosion of carbon monoxide. As mentioned before, the burning of carbon monoxide within the cupola is an oxidative reaction which would be self-defeating in that it would, if conducted in the melting zone, disturb the desired chemistry of the cupola reaction. Moreover, the equipment disclosed in the patent is quite intricate and, should malfunction occur, a potentially hazardous situation may well arise.

All of the foregoing problems are solved by the present invention.

SUMMARY OF THE INVENTION One of the objects of this invention is to provide improved apparatus and method to exhaust cupola gases from a cupola.

Another of the objects of this invention is to provide improved apparatus and method to economically and safely exhaust cupola gases from a cupola.

A further object of this invention is to provide improved apparatus and method for exhausting cupola gases from a cupola producing minimum quantities of gas to be handled subsequently by a gas cleaning and treating system.

Still a further object of this invention is to provide improved apparatus and method for exhausting cupola gases from a cupola whereby the chemistry of the operation occurring within the cupola is left undisturbed.

Yet another object of this invention is to provide improved apparatus and method whereby an existing cupola can be easily and economically modified to permit the safe exhaust of cupola gases therefrom producing minimum amounts of gases subsequently to be handled in a gas cleaning and treating system.

Still another object of this invention is to provide improved apparatus and method whereby to eliminate the cap or damper conventionally required when a gas cleaning and treating system is incorporated in a cupola installation.

Other and further objects of this invention will become apparent during the course of the following description and by reference to the accompanying drawing and the appended claims.

Briefly, we have discovered that the foregoing objects can be attained by permitting combustion air to enter the cupola through the lower portion of the charging opening in small quantities sufficient only to sweep or exhaust the cupola gases from the cupola and to burn the combustible matter contained therein with little or no excess air, by providing a gas takeoff directly adjacent the charging opening, by providing burners in the cupola adjacent the charging opening to ignite the eupola gases before they enter the gas takeoff, and by leading the ignited mixture of cupola gases and combustion air to a combustion chamber external to the cupola for further oxidation of the combustible matter in said gases before the gases are passed through the gas cleaning and treating system. Thereby, the chemistry of the operation in the cupola is left undisturbed, formation of dangerous quantities of carbon monoxide within the cupola is prevented, and the quantities of gas passing through the gas cleaning and treating system are minimized.

BRIEF DESCRIPTION OF THE DRAWING Referring now to the only FIGURE of the drawing, therein is shown the discharge stack mounted on the cupola, partially broken away to show the charging opening and adjacent gas takeoff leading to the combustion chamber ahead of the gas cleaning system.

, DESCRIPTION OF THE PREFERRED EMBODIMENT Cupola 1 is seen as having charging opening 2 through which a charge of scrap iron and coke may be introduced to form a bed 3 of such reactive material within the furnace portion 4, the said cupola 1 being surmounted by a discharge stack 5.

Directly opposite charging opening 2, an opening 6 is provided in the wall of cupola 1, said opening 6 communicating with a gas takeoff duct 7, and the latter in turn communicating with secondary combustion chamber 8. Gas takeoff duct 7 may be at an elevation adjacent the lower midportion of charging opening 2 as shown, or may be at an elevation adjacent the upper portion of charging opening 2. Mounted with cupola 1, adjacent charging opening 2 and generally at a level between gas takeoff duct 7 and the top of the bed 3 of reactive material are one or more burners l2, directing flames 13 toward the said gas takeoff duct 7 as shown diagrammatically in the drawing.

Secondary combustion chamber 8 may include one or more burners (not shown), to insure complete combustion of all combustible matter in the cupola gases entering the said secondary combustion chamber 8. Outlet duct 9 of secondary combustion chamber 8 leads to a conventional gas cleaning and treating system including a fan for producing a draft (not shown but well known to those familiar with this art).

Ordinarily, the dimensions of charging opening 2 will be determined by the requirement for conveniently introducing the charge of scrap iron and coke into the cupola 1, and the charging opening 2 in the preferred embodiment is always open, no door being provided therefor unlike certain prior art structures. The capacity of the fan is chosen, with a view to the quantity of air used in the tuyeres of the cupola in the normal course of operation, so that only enough combustion air 10 is drawn through the lower portion of the charging opening 2 to sweep or exhaust the cupola gas through opening 6 into gas takeoff duct 7 and thence into combustion chamber 8 and to burn the carbon monoxide and other combustible matter in the cupola gas with little or no excess air. Burners 12 function to ignite the mixture of combustion air 10 and combustible matter such as carbon monoxide in the cupola gases when the concentration of such combustible matter exceeds the lower combustion limit thereof, thereby to prevent explosion in the gas cleaning and treating system and to burn off any oil driven off from the scrap charge.

The upper portion of stack does not require the conventional cap or damper ordinarily associated with cupola installations having a gas cleaning and treating system.

In operation, the charge of scrap iron and coke is in-. troduced through charging opening 2 to form a bed 3 within the furnace portion 4 of cupola I. Cupola l is lighted in the nonnal manner and the fan of the gas cleaning and treating system is started to produce the required draft. Cupola gas generated within the cupola 1 mixes with combustion air entering through the lower portion of charging opening 2. When the concentration of combustible matter such as carbon monoxide in the cupola gas is below its lower combustible limit, combustion air 10 merely dilutes said combustible material further. When the concentration of combustible matter within the cupola gas is above its lower combustion limit in air, the mixture of cupola gas and combustion air is ignited by means of burners 12 within the cupola 1 above the bed 3 of reactive material. The mixture of cupola gas and combustion air 10, ignited as aforesaid, is swept out of the eupola 1 through opening 6 into gas takeoff duct 7 and thence into secondary combustion chamber 8. Burners in secondary combustion chamber 8 may be operated in order to insure complete combustion of all combustible matter in the cupola gases, and the completely combusted cupola gases exiting secondary combustion chamber 8 are then lead to the gas cleaning and treating system through duct 9.

In the foregoing manner, formation of dangerous quantities of unignited combustible matter such as carbon monoxide in the cupola l is prevented. All combustible matter in the cupola gases is essentially oxidized before the cupola gases enter the gas cleaning and treating system for treatment therein and subsequent discharge to the atmosphere, thus insuring compliance with various laws and ordinances, and the quantities of gases required to be passed through the gas cleaning and treating system are minimized.

We claim:

1. Apparatus for ventilating cupola gases from a cupola, said cupola gases being generated in a bed of reactive material within the cupola and containing combustible matter, said cupola having a charging opening above the bed of reactive material, said apparatus comprising:

a. gas takeofi conduit means communicating with the interior of said cupola adjacent said charging opening above said bed of reactive material,

b. fan means to draw a current of air through the lower portion of said charging opening into said cupola over said bed of reactive material thereby to form a mixture of said air with said cupola gases within said cupola above said bed of reactive material, said fan means further moving said mixture of air and cupola gases out of said cupola and into said gas takeoff conduit means,

. combustion means mounted within the cupola and interposed between said charging opening and said gas takeoff conduit means above said bed of reactive material, said combustion means igniting said mixture of air and cupola gases within said cupola prior to the movement of said mixture of air and cupola gases into said gas takeoff conduit means.

Apparatus as in claim 1, further comprising:

said gas takeoff conduit means communicating with the interior of said cupola at a location opposite said charging opening, whereby said mixture of air and cupola gases are moved generally in a horizontal direction over and across said bed of reactive material.

3. Apparatus as in claim 1, further comprising:

d. second combustion means having an inlet end and an outlet end,

e. said gas takeoff conduit means communicating with the inlet end of said second combustion means,

f. the outlet end of said second combustion means being adapted to communicate with a gas cleaning and treating system.

4. Apparatus as in claim 3, further comprising:

g. said fan means having a suction side, said suction side communicating with the outlet end of said second combustion means.

5. Method of ventilating cupola gases from a cupola, said cupola gases being generated in a bed of reactive material within the cupola and containing combustible matter, said method comprising the following steps:

a. admitting a current of air into said cupola at a location generally above the bed of reactive material, said current of air being admitted at a rate sufficient only to combuat said combustible matter with substantially no exccaa air,

nited mixture of air and cupola gases from said cupola.

7. Method as in claim 6, said draft drawing the gases produced by the said ignited mixture of air and cupola gases through a gas cleaning system.

8. Method as in claim 5, said current of air passing generally in a horizontal direction over and across said bed of reactive material toward the location in said cupola from which said ignited mixture of air and cupola gases is withdrawn. 

1. Apparatus for ventilating cupola gases from a cupola, said cupola gases being generated in a bed of reactive material within the cupola and containing combustible matter, said cupola having a charging opening above the bed of reactive material, said apparatus comprising: a. gas takeoff conduit means communicating with the interior of said cupola adjacent said charging opening above said bed of reactive material, b. fan means to draw a current of air through the lower portion of said charging opening into said cupola over said bed of reactive material thereby to form a mixture of said air with said cupola gases within said cupola above said bed of reactive material, said fan means further moving said mixture of air and cupola gases out of said cupola and into said gas takeoff conduit means, c. combustion means mounted within the cupola and interposed between said charging opening and said gas takeoff conduit means above said bed of reactive material, said combustion means igniting said mixture of air and cupola gases within said cupola prior to the movement of said mixture of air and cupola gases into said gas takeoff conduit means.
 2. Apparatus as in claim 1, further comprising: d. said gas takeoff conduit means communicating with the interior of said cupola at a location opposite said charging opening, whereby said mixture of air and cupola gases are moved generally in a horizontal direction over and across said bed of reactive material.
 3. Apparatus as in claim 1, further comprising: d. second combustion means having an inlet end and an outlet end, e. said gas takeoff conduit means communicating with the inlet end of said second combustion means, f. the outlet end of said second combustion means being adapted to communicate with a gas cleaning and treating system.
 4. Apparatus as in claim 3, further comprising: g. said fan means having a suction side, said suction side communicating with the outlet end of said second combustion means.
 5. Method of ventilating cupola gases from a cupola, said cupola gases being generated in a bed of reactive material within the cupola and containing combustible matter, said method comprising the following steps: a. admitting a current of air into said cupola at a location generally above the bed of reactive material, said current of air being admitted at a rate sufficient only to combust said combustible matter with substantially no excess air, thereby to form a mixture of air and cupola gases within said cupola above said bed of reactive material, b. igniting said mixture of air and cupola gases within said cupola above said bed of reactive material, c. withdrawing said ignited mixture of air and cupola gases from a location in said cupola adjacent the location at which the current of air is admitted into said cupola.
 6. Method as in claim 5, wherein is provided a draft to draw said current of air into said cupola and to withdraw said ignited mixture of air and cupola gases from said cupola.
 7. Method as in claim 6, said draft drawing the gases produced by the said ignited mixture of air and cupola gases through a gas cleaning system.
 8. Method as in claim 5, said current of air passing generally in a horizontal direction over and across said bed of reactive material toward the location in said cupola from which said ignited mixture of air and cupola gases is withdrawn. 